Method of controlling the tension of strands



Aug. l,-19 s. L. GERHARD METHOD OF CONTROLLING THE TENSION 0F STRANDS Filed Dec. 2, 1943 BY M W H ATTORNEY Patented Aug. 1, 1944 METHOD or CONTROLLING THE TENSION F s'rrtsnns Sherman L. Gerhard, La Grange, Ga., assignor to United States Rubber Company, New York, N. Y., a corporation of New Jersey Application December 2, 1943, Serial No. 512,571

4 Claims. ('01. 242 147) This invention relates to a method of controlling automatically the tension of an advancing strand, and is well adapted for broad application to control the tension of a strand of yarn, cord, rope, cable or extruded filament.

Numerous tension devices have been employed heretofore to increase the tension of an advancing strand, but the trouble with most'of these devices is that they'increase the tension of the strand but fail to control the tension automatically so as to impart the advancing strand More specifically the present method contem' plates the use of a drum or other member having an arcuate surface and supported to rotate about an axis concentric to such surface. It also contemplates the use of means for exerting a constant torque upon the drum or the like to continuously urge it in onedirection, so that the tendency of this drum to rotate in one direction under the constant torque will be balanced against the total retarding force. exerted upon the strand at the instant it, leaves the drum. This result is secured by advancing the strand toward the drum along its axis of rotation, so

' that the pull exerted upon the strand to advance the supply source more readily than another portion of this strand, so that the tension ofthe strand as it advancesalong a definite path of travel may vary considerably.

It is a simple matter to place a tension device along such path of travel to increase the tension of the strand, but if the action of the tension device is to exert substantially the same retarding force on all parts of the advancin strand, it will increase the tension of the strand without imparting to the strand uniform tenson.

The present method overcomes this difficulty andprovides a simple and practical method for imparting a uniform tension to an advancing strand. This tension may be as low or as high as'deslred since a desiredconstant force is established, and then a balance is maintained between this force in one direction and the total tension upon the strand as it advances in the opposite direction. I

Since, as above stated, the tension of a strand may vary'considerably as it approaches atension device such as herein contemplated and is to be constant upon leaving such device, then this device should operate automatically to impart to the strand a varying retarding force that will equal the difi'erence between the tension of the strand as it arrives at this tens on device and the constant tension of the strand as it leaves the tension device.

In carrying out the present method a drum or arcuate member adapted to rotate about a central axis is employed, and a -weight is employed to exert a constant torque upon the drum to rodevice.

it to this position will not produce a torque tending to turn the drum. The strand is then advanced outwardly to the periphery of the drum to be dragged over an arc of the surface of the drum, the lengthof which are will vary as the drum rocks back and forth to establish a'b"alance reaches the drum plus the additional tension placed upon the strand as it drags over an arc of the drum surface. The varyin tensionof the strand as it reaches the drum will cause the drum to rock back and forth to decrease or increase the length of the arc over which the-Jstrand drags so that the tensionv of the strand as it leaves th 1 and i Fi 3 is an end view of a modificaton of the apparatus of Fig. 2.

In the construction shown in Figs. 1 and 2 of I the drawing l0 designates a drum-having the the drum In there is disposed a thread guide comprising the upright ll having the pig-tail I5 formed at the upper end thereof and disposed o 19 formed in the annular wallof the drum 10,-

to drag around upon a portion 'of the outer periphery of the drum to thereby exert a retardin force upon this strand. The strand I6 upon leaving the drum I may pass to any form of takeup means such for example as the takeup spool 20 which is rotatably supported at 2| and is driven in the direction indicated by the arrow by the belt 23 passing around the pulley 22.

It will be seen from the construction so far described by reference numerals that as the strand I6 is pulled forward by the rotation of the takeup spool 20, it will exert a turning force upon drum l0 tending to rotate the same in a clockwise direction viewing Fig. 2. The rotation of the drum III in this direction is yieldingly opposed, by a constant torque which tends to rotate the drum in the opposite direction. This torque can be supplied by a suspended weight, or. a torque which will be approximately constant can be supplied by a relatively long coiled spring. In the construction shown the desired torque is supplied by the cord 24 one end of which is secured to the drum ill at 25. .This cord which is wound one or more times around the drum III as shown in Figs. 1 and 2 has a downwardly extending end.

to which the weight W is attached. This weight preferably has the auxiliary weights shown resting thereupon to regulate the downward pull exerted upon the drum ill by the cord 24 to rotate the drum in an anti-clockwise direction with a constant torque.

The construction is such that during the operation of this tension device the drum l0 will rock back and forth as indicated by the arrow in'Fig. 2 and thereby increase or decrease the length of the arc of the drum surface over which the strand l6 slides, to thereby vary the retarding force which is imparted to this strand as the result of its frictional engagement with the drum surface.

The purpose in supplying the strand l6 to the drum in by advancing it thereto in a direction along the axis ofrotation of the drum or at a right angle to the plane in which the drum rotates, is so that the pull required to advance the strand to the drum will not exert a torque that will tend to turn the drum.- The strand l6 after passing through the pig-tail guide passes outwardly to the outer periphery of the drum to drag upon such outer periphery as above stated. As a result of this construction, the entire pulling force exerted upon the strands l6 at the point T at which it leaves the outer periphery of the drum tends to rotate the drum in a clockwise direction,

and this pull is opposed and balanced by the torque in the opposite direction exerted by the weight W. As the pull required to advance the strand iii to the pigtail l5, and which pulling force is herein indicated by T', varies the drum Ill will rotate in one direction or the other to vary the length of the arc of frictional contact of the strand with the outer periphery of the cated by T then that the thread passing therethrough will travel drum, to thereby vary the frictional retarding force herein indicated by F.

If the torque exerted upon drum ill by the weight W to turn this drum in a counterclockwise direction is indicated by W, and the tension upon the strand l6 as it leaves the drum in is indi- If the force required to advance the strands l6 to the pigtail I5 is indicated by T and the retarding force which is produced by the friction between the strand lfi and the drum 10 as the strand is dragged over the outer surface of this drum is indicated by F then As T varies due to the variation in the force required to advance the strand 16 to the drum, the drum will automatically rotate to vary the friction F to maintain the equilibrium T'+F=T=W This is what is desired to cause the strand l6 to leave the drum l0 under a constant tension irrespective of the variations in the tension of the yarn at T.

In the construction shown the guide l5 has been provided directly in front of the drum. and

.amount of friction required, the number of such loops will be automatically determined by W and T, in order to produce the amount of friction between the drum and the strand it necessary to maintain equilibrium. 7

In the modified construction of Fig. 3 the operation is substantially the same as that shown in Figs. 1 and 2 except that the cord 24' is shown as wound upon a drum 21 of smaller diameter than that of the drum l0 about which the strand I6 is wrapped. Furthermore the drum I0 is given a squirrel-caged construction having the free running rollers 28 arranged so that the strand IE will engage these anti-friction rollers instead of sliding upon the surface of the drum as in the case of Figs. 1 and 2. In this construction of Fig. 3 in which the yarn l8 rests upon the rollers 28, the drag which the drum places upon the yarn will depend upon the force required to turn these rollers.

It will be seen from the foregoing that by employing the present method any desired tension may be imparted to the yarn l6 as it leaves the drum. I0 provided it is greater than the entering tension T.

Having thus described my invention, what I claim and desire to protect by Letters Patent is:

1. The method of controlling the tension of an advancing strand, which consists in providing a rotating drum and exerting a constant torque that tends to rotate the drum about its central axis, supplying a strand to approach the drum along its axis of rotation and then outwardly to the periphery of the drum to drag over an arc of the drum surface so that this are of contact will vary as the drum rotates, and pulling the strand from the drum in a direction to decrease this are while said torque tends to increase the The drum I0 is shown as arc, so that the tension of the strand as it leaves the drum will equal said constant torque.

2. The method of controlling the tension of anadvancing strand, which consists in providing a rotating drum and exerting a constant torque that tends to rotate the drum about its central axis, supplying a strand to approach the drum along its axis of rotation and then outwardly to the periphery of the drum to drag over an arc of the drum surface in a direction to turn the drum against said torque, so that the tension of the strand as it leaves the drum will equal said constant torque.

3. The method of controlling the tension of an advancing strand, which consists in providing an arcuate member adapted to rotate about its central axis, exerting a constant torque that tends to rotate said member, supplying a strand to approach said member along its axis of rotation and then outwardly to the periphery of the arcuate 20 member to drag over an arc thereof so that this are of contact will vary as the arcuate member rotates, and pulling the strand therefrom in a direction to decrease this are while said torque tends to increase this arc, so that the tension of the strand as it leaves the arcuate member will equal said constant torque.

4. The method of controlling the tension of an advancing strand, which consists in providing an arcuate member adapted to rotate about its central axis, exerting a constant torque that tends to rotate said member, supplying a strand to approach said member at a right angle to the plane in which the arcuate member rotates and then outwardly to the periphery of the arcuate memher to drag over an arc thereof so that this are of contact will vary as the arcuate member rotates, and pulling the strand therefrom in a direction to decrease this arc while said torque tends to increase this arc, so that the tension of the strand as it leaves the arcuate member will equal said constant torque.

i SHERMAN L. GERHARD. 

